This application claims priority to Italian application MI2000A001986 filed on Sep. 12, 2000.
The present invention relates to novel variants of an allergen of mites of the species Dermatophagoides pteronyssinus. 
More particularly, the present invention relates to the amino acidic sequences of hypoallergenic variants of the allergen Der p 2, obtained by site-specific mutagenesis of the nucleotidic sequence encoding for said allergen. The hypoallergenic variants can be used in the specific immunotherapy of allergic pathologies caused by dust mites.
Allergies are immediate hypersensitivity reactions caused by the production of IgE class antibodies following contact with allergens. IgEs bind to specific receptors located at the surface of effector cells (basophiles and mast cells) and when exposed again to the allergen they induce degranulation of said cells, which release mediators such as histamine and leukotrienes, responsible for the known symptoms of allergies: rhinitis, conjunctivitis, atopic dermatitis and asthma.
Dermatophagoides pteronyssinus and Dermatophagoides farinae are two similar species of mites present in house dust. The allergens deriving from these arthropods have remarkable importance in clinic.
Nine different types of mites allergens have up to now been identified, the main two being Der p 1 (Der f 1) and Der p 2 (Der f 2), each of them immunoreacting with IgEs in about 80% of allergic subjects.
The allergen Der p 2 (whose nucleotidic sequence is identified in GenBank under the access code AF276239) is a protein consisting of 129 amino acidic residues with a molecular weight of about 14 kD, which contains 3 disulfide bonds essential for its immunogenicity [1, 2]. It has no sequence homology with any other known protein, except Der f 2 (GenBank access code D10449).
The only etiological treatment of allergies is represented by specific hyposensitizing immunotherapy (SIT). This consists in administering increasing doses of the substance which causes the allergy, thus inducing gradual desensitization to said substance in the patient (3).
Immunotherapy however, although constituting an established treatment for allergies, is not completely free from risks (4).
As even serious side effects can occur during such therapy, reasearches have been focused towards the use of non-injective routes (oral/sublingual) for the administration of vaccines and the production of hypoallergenic variants of the proteins used as vaccines, obtained through modification of the allergens by chemical treatments or site-specific mutagenesis [5].